Secretions of the Small Intestine, Liver, Gall Bladder and Pancreas

Question 1

The small intestine

Answer 1

Question 2

GIP is

Answer 2

Gastric Inhibitory peptide/ glucose dependent insulinotrophic peptide

Question 3

The small intestine governs

Answer 3

majority of chemical digestion,, absorption of nutrients, electrolytes and water

Question 4

Primary Secretions of the small intestine are:

Answer 4

• intestinal juice (mucous/HCO3-)
• pancreatic juice (digestive enzymes)
• bile (bile salts)

Question 5

Key endocrine hormones in the small intestine:

Answer 5

• secretin
• cholecystokinin (CCK)
• glucose dependent insulinotrophic
  peptide (GIP)
• regulates bile and pancreatic
  secretion

Question 6

Secretory cells of the small intestine

Answer 6

Question 7

Secretory cells of the small intestine:

Answer 7

• Villi: houses absorptive enterocytes
  and mucus secreting goblet cells
• Intestinal Glands:
  
  • Enterocytes (isotonic fluid)
  • Enteroendocrine cells
    (hormones)
  • Paneth cells (lysozymes)
• In the duodenum only:
  - brunner’s glands (only in
  duodenum) secrete alkaline
  mucus and HCO3-

Question 8

Stem cell renewal of epithelial cells:

Answer 8

insert diagram
- rapid regeneration rate (3-6 days)
- rapid regeneration rate makes the
cells vulnerable to radiation and
chemotherapy

Question 9

CCK (I cells) function

Answer 9

stimulate pancreatic and gallbladder secretion

Question 10

Secretin (S cells) function

Answer 10

stimulate pancreatic and biliary bicarbonate secretion

Question 11

GIP (K cells) function

Answer 11

may inhibit acid secretion/ stimulate insulin release

Question 12

Exocrine pancreatic juice consists of

Answer 12

bicarbonate and digestive enzymes

Question 13

Pancreas

Answer 13

Question 14

Pancreas only has endocrine function.

True or False?

Answer 14

False
Endocrine and Exocrine

Question 15

Pancreas is regulated by both hormonal and neural mechanisms via

Answer 15

subdivision of cranial nerve X (vagus)

Question 16

Exocrine pancreas secretes

Answer 16

pancreatic juice containing bicarbonate rich secretion (pH8) and digestive enzymes essential for normal digestion and absorption

Question 17

The pancreas consists of

Answer 17

glandular epithelial clusters

Question 18

99% of pancreatic structure is

Answer 18

exocrine acinar clusters secreting pancreatic juice

Question 19

Pancreatic Juice consists of

Answer 19

• water
• electrolytes
• sodium bicarb
• pro-enzymes

Question 20

1% pancreatic structure consists of

Answer 20

endocrine pancreatic islets
(Islets of langerhans) of 4 types of secreting cells: alpha, beta, delta, F cells

Question 21

Alpha cells in the Islets of Langerhans secrete

Answer 21

glucagon

Question 22

Beta cells in the Islets of Langerhans secrete

Answer 22

insulin

Question 23

Delta cells in the Islets of Langerhans secrete

Answer 23

somatostatin

Question 24

F cells in the Islets of Langerhans secrete

Answer 24

pancreatic polypeptide (PP cells)

Question 25

Exocrine Acinar clusters

Answer 25

Question 26

Regulation of exocrine pancreatic secretion

Answer 26

Acinar enzyme production: - Ach released via parasympathetic CNX (vagus) stimulation of CCK - trigger is chyme containing fat and protein products - produces lower volume of enzyme rich pancreatic juice Ductal Bicarb and Water: - Secretin - trigger is H+ in highly acidic chyme - produces plentiful, HCO3- rich, low enzyme pancreatic juice

Question 27

Pancreatic Proteolytic Enzymes are secreted in ------ form: - active - inactive

Answer 27

inactive

Question 28

Pancreatic Proteolytic enzymes are responsible for

Answer 28

the conversion of proteins to peptides

Question 29

Amylase hydrolyses

Answer 29

starch, glycogen and other carbs to form di/trisaccharides

Question 30

Lipases hydrolyse

Answer 30

fat into fatty acids and monoglycerides

Question 31

Nucleases digest

Answer 31

RNA and DNA to nucleic acids

Question 32

Trypsin inhibitor prevents

Answer 32

activation of trypsin to prevent pancreatic digestion

Question 33

Activation of Proteolytic Enzymes: how are they produced?

Answer 33

inactive precursors called zymogens

Question 34

Activation of Proteolytic Enzymes: how is active trypsin formed?

Answer 34

small intestinal brush border enterokinase cleaves hexapeptide to form active trypsin from trypsinogen

Question 35

Activation of proteolytic enzymes: active trypsin purpose:

Answer 35

trypsin cleaves and activates other proteolytic enzymes

Question 36

What prevents autodigestion?

Answer 36

- trypsin inhibitor - process of pancreatic enzymes destroying its own tissues, resulting in inflammatory response

Question 37

Duct Secretion of Sodium Bicarbonate

Answer 37

Question 38

Duct secretion of sodium bicarbonate:

Answer 38

- secretin stimulates a high volume of HCO3- rich pancreatic juice - HCO3- secretion out of cell into the duct lumen is via CL-/HCO3- exchange at the apical cell membrane - Cl- is recycled out of the cell via the cystic fibrosis transmembrane conductance regulator CFTR Cl- channel under secretin stimulation via cAMP - Na+ is secreted transcellularly into the duct lumen following HCO3- secretion down electrochemical gradient, water follows by osmosis

Question 39

Regulation of Pancreatic Juice Secretion:

Answer 39

- Ach: vago-vagal gastro-pancreatic reflex, gastrin, secretin, CKK/pancreozymin

Question 40

Cystic Fibrosis and the Pancreas

Answer 40

- lack a functional Cl- channel in the luminal membrane, which results in defective ductal fluid secretion (CFTRE Cl-) - the ducts become blocked with precipitated ezymes and mucus and the pancreas undergoes fibrosis - blocked ducts impair secretion of needed pancreatic enzymes for digestion of nutrients, resulting in malabsorption

Question 41

Treatment of cystic fibrosis pancreas effects

Answer 41

- treatment of malabsorption includes oral pancreatic enzyme supplements taken with each meal

Question 42

Pancreatitis: - is - common cause

Answer 42

- inflammatory disease where pancreatic enzymes are activated within the pancreas and surrounding tissues, resulting in autodigestion - the most common causes: gallstones, alcohol misuse, which obstruct the pancreatic duct

Question 43

The role of bile in digestion

Answer 43

- bile salts emulsify fats for digestion by pancreatic lipase, solubilise fat digestion products into aggregations for absorption across the mucosa - elimination of waste products - bile pigment bilirubin from haem in RBC degradation (breakdown product stercobilin gives faecal brown) - cholesterol - drugs

Question 44

Synthesis and Secretion of Bile in the Liver

Answer 44

- bile is constantly synthesised by hepatocytes lining sinusoidal blood vessels in the liver acinus - hepatocytes are the key functional cell of the liver forming 80% of the liver mass - it drains into the blind ended canaliculi and into the L/R hepatic bile ducts of the liver

Question 45

Bile is stored in the gall bladder

Answer 45

Question 46

Bile Secretion Regulation

Answer 46

- CCK released in response to fat content of duodenum leads to: - gall bladder contraction - sphincter of hepatopancreatic ampulla - sphincter of oddi relaxation - secretin release in respons to acidic chyme - liver ductal secretion of HCO3-. H2O - minor role for vagal stimulation: bile flow, gall bladder contraction

Question 47

Enterohepatic circulation of bile salts

Answer 47

- bile salts are continuously recycled through active reabsorption within the ileum - 94% bile salts return via the portal vein to drive bile synthesis in the liver - many hydrophobic drugs are deactivated by the liver and excreted into bile; enterohepatic recycling frequently occurs, slowing the rate of drug elimination

Question 48

Enterohepatic circulation of bile salts

Answer 48

Question 49

Gall Bladder Disease:

Answer 49

Occurs in several forms, ranging from asymptomatic cholelithiasis [gallstones] to biliary colic [blockage of the cystic duct]. These disorder can affect different areas of the biliary tract

Question 50

Gallstones common causes:

Answer 50

- Excessive water and bile salt reabsorption from bile [supersaturation of bile] - Excessive cholesterol in bile causing precipitation [high fat diet]. - Inflammation of epithelium [low grade chronic infection].

Question 51

Gall Bladder Disease

Answer 51